Pityriasis rubra pilaris is generally believed to comprise more than a single entity and a classification scheme based on clinical characteristics and course has been proposed by Griffiths1 (Table 24-1).
Table 24-1 Classification Scheme of Pityriasis Rubra Pilaris (Types I–V According to Griffiths) ||Download (.pdf)
Table 24-1 Classification Scheme of Pityriasis Rubra Pilaris (Types I–V According to Griffiths)
Erythroderma with islands of normal skin (“nappes claires”), follicular hyperkeratosis, waxy diffuse palmoplantar keratoderma
Generalized, beginning on the head and neck, then spreading caudally
Often resolves within an average period of 3 years
Combination of follicular hyperkeratosis and ichthyosiform lesions on the legs, sparse scalp hair
Long duration (>20 years)
Similar to type I but appears in years 1 or 2 of life
Often resolves within an average period of 1–2 years
Prepubertal children; well-demarcated scaly, erythematous plaques on the elbows and knees, resembling localized psoriasis
Uncertain, some cases clear in the late teens
Begins in first few years, accounts for most familial cases; follicular hyperkeratosis, scleroderma-like appearance of the hands and feet
Chronic course, improvement with retinoids but relapses when stopped
Similar to type I with variable beginning; associated with acne conglobata, hidradenitis suppurativa and lichen spinulosus
May respond to antiretroviral triple therapy
Type I (classic adult) is the most common subtype with over 50% of all cases. Characteristically, patients present with an eruption of follicular hyperkeratotic papules that spread in cephalocaudal direction (Fig. 24-1). As the disease further evolves, a reddish orange, scaling dermatitis appears that often progresses to a generalized erythroderma over a period of 2–3 months (Fig. 24-2). A diagnostic hallmark of pityriasis rubra pilaris are sharply demarcated islands of unaffected skin (“nappes claires”) in a random distribution (Fig. 24-2B). Many patients develop a waxy, diffuse, yellowish keratoderma of the palms and soles (Fig. 24-3).3 Nail changes are not uncommon and include distal yellow–brown discoloration, nail plate thickening, splinter hemorrhages, and subungual hyperkeratosis. Eventually, the mucous membranes may be affected with a diffuse whitish appearance of the buccal mucosa as well as lacy white plaques and erosions. Hair and teeth are normal.
Acuminate follicular papules of pityriasis rubra pilaris. Close-ups of discrete (A) and confluent (B) lesions.
Generalized pityriasis rubra pilaris (A) with a reddish orange, scaling dermatitis, and islands of normal skin (“nappes claires”), shown in more detail in (B).
Keratoderma in pityriasis rubra pilaris. Palmar (A) and plantar (B) erythema and waxy hyperkeratosis are frequent manifestations. Sometimes, there is an orange–yellow tint.
Type II is an atypical variant with onset in adult age. Areas of follicular hyperkeratosis as well as ichthyosiform scaling, especially on the legs, dominate the clinical picture. This variant lacks the typical cephalocaudal progression observed in type I, and there is less tendency for the patients to become erythrodermic. Sparseness of the scalp hair is occasionally seen.
Type III (classic juvenile) typically begins in years 1 or 2 of life and shows all the morphological features of type I (Fig. 24-4).
Juvenile pityriasis rubra pilaris. A. Confluence of lesions leads to extensive erythroderma. B. Characteristic scattered islands of unaffected skin are evident. So is the plantar hyperkeratosis.
Type IV (circumscribed juvenile) affects approximately 25% of the patients. This type usually presents several years after birth and is characterized by well-demarcated hyperkeratotic erythematous plaques on the elbows and knees, resembling localized psoriasis. According to Griffith,1 these lesions do not progress to the widespread types I and III. Yet, some cases show marked palmoplantar keratoderma.
Type V is an atypical variant of juvenile pityriasis rubra pilaris that usually presents in the first few years of life and has a more chronic course. This type is distinguished by follicular hyperkeratosis with only minimal erythema and a scleroderma-like appearance of the hands and feet. Most cases of familial pityriasis rubra pilaris belong to this type, which may even represent a different clinical entity sharing features with several poorly defined ichthyotic disorders such as follicular ichthyosis and the erythrokeratodermas.
Other reports have described a type VI variant associated with HIV infection. The clinical features of this variant are similar to type I but with increased severity and additional manifestations of acne conglobata, hidradenitis suppurativa, and lichen spinulosus.
There have been rare cases of a pityriasis rubra pilaris-like eruption, clinically and histologically, in patients with dermatomyositis, often associated with internal neoplasia. Concomitant rheumatologic disorders, mainly inflammatory polyarthritis, have also been reported. In addition, numerous other noncutaneous diseases were considered to be related to pityriasis rubra pilaris, which are probably all fortuitous.
Pathological findings in pityriasis rubra pilaris vary according to the duration of the disease. The findings are most likely to be diagnostic in the acute phase, when hyperkeratosis, acanthosis with broad short rete ridges and alternating orthokeratosis and parakeratosis oriented in both horizontal and vertical directions can be observed. Usually, there is a sparse superficial, perivascular lymphocytic infiltrate in the underlying dermis. Keratinous plugs of the follicular infundibula as well as perifollicular areas of parakeratosis may also be present. A prominent granular layer and dilated, but not tortuous capillaries are features that help to distinguish pityriasis rubra pilaris from psoriasis, its most important differential diagnosis.